This invention relates to apparatus and methods for measuring radiation or the characteristics of materials from the manner in which they react with radiation.
In one class of apparatuses and methods for measuring radiation or characteristics of materials from the manner in which they react with radiation, light of certain selected wavelengths is detected and the range of wavelengths is varied across a spectrum to provide an electrical signal corresponding to the light in each of the wavelength bands. The electrical output is then analyzed and is used to provide an indication of the nature of the light which has been received and, in some instances, the manner in which the light from a known source was altered by its interaction with a material, in which case the light is analyzed to determine the characteristics of the material.
In one type of prior art apparatus and method of this class, the detector is a photomultiplier that is controlled in temperature to provide a relatively high signal for a relatively low amount of flux. In such photomultipliers the electrical signal resulting from the light intensity available for usual studies is sufficiently strong for use.
Usually devices which measure the characteristic of light radiation from an external unknown source, which are referred to hereinafter as spectroradiometers, are used only for that purpose and devices which utilize light from a known source to determine the characteristics of a material interacting with the light are also stand-alone single-purpose units, referred to in this specification as photoradiometers.
The prior art apparatuses have several disadvantages such as: (1) they are relatively large; (2) they are expensive; (3) they require large amounts of power; (4) they are not portable nor easily used in the field, because of the large weight and power requirements; and (5) different stand-alone instruments must be used for spectroradiometry and photoradiometry, thus increasing the cost to the scientist.